Dicarboxylic acids, e.g. adipic and dodecanedioic, are produced by the oxidation of cyclic hydrocarbons, e.g. ketones and alcohols and the further oxidation of these by nitric acid to the dicarboxylic acids. These processes produce dibasic acid waste products which become part of waste streams that must be discarded. Disposal of these waste streams has been expensive and detrimental to the ecology campaign which is of immediate interest since these by-products are currently burned or buried.
Dodecanedioic acid, used in some nylon manufacture, is made by nitric acid oxidation of C.sub.12 cyclic hydrocarbon. This process also produces C.sub.4 to C.sub.12 dibasic acid waste products that also must be discarded.
Various techniques are available for separation, recovery and purification of the dibasic acids by crystallization. The preparation of esters from the purified acids is a well-known process. The preparation of esters from acids not crystallized by reaction with alcohols commonly produces yellowish esters, whose color is accentuated by alkaline conditions and by heating, particularly under the alkaline conditions often used for transesterifications.